Thank you Benny,
from engine:
2019-01-31 14:22:36,884Z INFO [org.ovirt.engine.core.bll.storage.connection.ConnectStorageToVdsCommand] (default task-6344) [d8697f85-8822-4588-8d7c-1ed6a5b1d9ca] Running command: ConnectStorageToVdsCommand internal: false. Entities affected : ID: aaa00000-0000-0000-0000-123456789aaa Type: SystemAction group CREATE_STORAGE_DOMAIN with role type ADMIN
2019-01-31 14:22:36,892Z INFO [org.ovirt.engine.core.vdsbroker.vdsbroker.ConnectStorageServerVDSCommand] (default task-6344) [d8697f85-8822-4588-8d7c-1ed6a5b1d9ca] START, ConnectStorageServerVDSCommand(HostName = hp-1.test.lab, StorageServerConnectionManagementVDSParameters:{hostId='e45920ea-572d-4d52-917d-207d82c1d305', storagePoolId='00000000-0000-0000-0000-000000000000', storageType='ISCSI', connectionList='[StorageServerConnections:{id='null', connection='10.10.8.13', iqn='iqn.2004-04.com.qnap:ts-ec1280u-rp:iscsi.test.f35296', vfsType='null', mountOptions='null', nfsVersion='null', nfsRetrans='null', nfsTimeo='null', iface='null', netIfaceName='null'}]', sendNetworkEventOnFailure='true'}), log id: 347096b2
2019-01-31 14:22:38,112Z INFO [org.ovirt.engine.core.vdsbroker.vdsbroker.ConnectStorageServerVDSCommand] (default task-6344) [d8697f85-8822-4588-8d7c-1ed6a5b1d9ca] FINISH, ConnectStorageServerVDSCommand, return: {00000000-0000-0000-0000-000000000000=0}, log id: 347096b2
2019-01-31 14:22:38,437Z INFO [org.ovirt.engine.core.vdsbroker.vdsbroker.GetDeviceListVDSCommand] (default task-6344) [0ef49cb3-8b81-4f65-8a9d-aa5d57ca6575] START, GetDeviceListVDSCommand(HostName = hp-1.test.lab, GetDeviceListVDSCommandParameters:{hostId='e45920ea-572d-4d52-917d-207d82c1d305', storageType='ISCSI', checkStatus='false', lunIds='null'}), log id: 2fdc334a
2019-01-31 14:22:39,694Z INFO [org.ovirt.engine.core.vdsbroker.vdsbroker.GetDeviceListVDSCommand] (default task-6344) [0ef49cb3-8b81-4f65-8a9d-aa5d57ca6575] FINISH, GetDeviceListVDSCommand, return: [], log id: 2fdc334a
In vdsm I can't find something related to this operation...
It feels like is not getting the luns from the target, although from a different client ( windows machine) i can successfully connect and map the lun.